Copper iron composite oxide catalysts have been prepared by co-precipitation method. The catalytic activity and stability of the catalysts on CO oxidation were evaluated by using a microreactor-GC system. The results indicated that the copper iron composite oxide catalysts exhibited obviously high stability and catalytic activity on CO oxidation at low temperature. The effect of the calcination temperature, the molar ratios of copper to iron, the specific surface areas and the particle sizes on the catalytic activity of the catalysts was investigated in this paper.